The sirtuins are an evolutionarily ancient class of enzymes present in all organisms from prokaryotes to humans (Sauve (2010) Biochim. Biophys. Acta 1804: 1591). One demonstrated function of these enzymes is protein deacylation. Sirtuins are capable of deacylating many different proteins, but the process is absolutely dependent on nicotinamide adenine dinucleotide (NAD), and the common products of all sirtuin mediated deacylation reactions are nicotinamide and O-acetyl-adenosine diphosphate ribose (OAADPR). While nicotinamide is involved in many different biological reactions, biosynthesis of OAADPR is only known to occur via sirtuin mediated protein deacylation (Tanner et al. (2000) Proc. Natl. Acad. Sci. USA 97: 14178; Tong and Denu (2010) Biochem. Biophys. Acta 1804: 1617; Lee et al. (2008) Anal. Biochem. 383: 174).
There is evidence that OAADPR, presumably as the mixture of 2′ and 3′ isomers, functions as an intracellular second messenger (Wolberger and Hoff (2005) Nat. Struct. Mol. Biol. 12: 560). Microinjection experiments showed that starfish oocyte maturation could be delayed or halted by infusion of OAADPR (Borra et al. (2002) J. Biol. Chem. 277: 12632). Several intracellular proteins have been shown to bind OAADPR, and mechanisms for the regulation of gene transcription have been proposed (Norris and Boeke (2010) Genes Dev. 24: 115). Additionally, enzymes that catalyze the degradation of OAADPR are known (Ono et al. (2006) Proc. Natl. Acad. Sci. USA 103: 16687). The identification of additional proteins that interact with OAADPR is an area of active investigation (Tanner et al. (2000) Proc. Natl. Acad. Sci. USA 97: 14178).
Previously, three groups prepared isolable amounts of OAADPR. Schramm et al. performed an acyl transfer from an 18 amino acid peptide bearing a Nε-acetyllysine residue to NAD using a bacterial sirtuin enzyme as the catalyst (Sauve et al. (2001) Biochemistry 40: 15456). Borra and Denu used a similar enzymatic approach to prepare OAADPR, employing a Drosophila sirtuin as the catalyst, while Moss used human SIRT1 as the catalyst (Borra et al. (2002) J. Biol. Chem. 277: 12632; Ono et al. (2006) Proc. Natl. Acad. Sci. USA 103: 16687). Comstock and Denu performed the first total synthesis of OAADPR using a 12-step sequence that allowed them to prepare a mixture of 2′-O-acetyl-ADP ribose and 3′-O-acetyl-ADP ribose isomers, as well as several amide isosteres (Comstock and Denu (2007) Org. Biomol. Chem. 5: 3087). Denu and Schramm both showed that the regioisomers 2′-O-acetyl-ADP ribose and 3′-O-acetyl-ADP ribose interconverted in aqueous solution at pH=7.5, giving a 1:1 ratio of regioisomers at equilibrium (Jackson and Denu (2002) J. Biol. Chem. 277: 18535).
The use of a sirtuin catalyzed biochemical reaction to generate OAADPR requires enzymatically active sirtuin preparations and is commensurately limited in scale and economy. The efficient preparation of OAADPR from readily available starting materials using a simple, inexpensive, and easily scaled chemical synthetic method would provide an improved method of producing this compound for its multiple uses in biotechnology and the biological arts.